AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Friday Sessions
       Session MI+TF-FrM

Paper MI+TF-FrM11
MOCVD Growth of Co@sub x@Zn@sub 1-x@O on R-plane Sapphire: Structure, Composition, and Magnetic Properties

Friday, November 8, 2002, 11:40 am, Room C-205

Session: Magnetic Thin Films and Surfaces
Presenter: A.C. Tuan, University of Washington
Authors: A.C. Tuan, University of Washington
T. Droubay, Pacific Northwest National Laboratory
J.W. Rogers, Pacific Northwest National Laboratory
S.A. Chambers, Pacific Northwest National Laboratory
Correspondent: Click to Email
We have grown Al-doped Co@sub x@Zn@sub 1-x@O films by MOCVD for application as a spintronic material. Films were grown at substrate temperatures between 750 and 825 K at a growth rate of ~6 nm/min. XRD and RBS show that up to 35% of the Zn cations can be substituted with Co without disrupting the wurtzite crystal structure of ZnO. Furthermore, XRD pole figures indicate that the films are of near-single crystal quality. Comparison of the Co 2p core-level XPS from our Co@sub x@Zn@sub 1-x@O films with reference spectra for Co metal, Co(II), and Co(III) shows that the Co ions are in the +2 oxidation state. XPS also shows that there is no carbon contamination in the bulk of the film, which suggests that the organometallic precursors are completely oxidized/pyrolyzed. Since the Co distribution in the material strongly affects the magnetic properties, we performed SIMS depth profiling, which confirmed that the Co and Al constituents are uniformly distributed throughout the film and show no segregation at either the interface or the surface. In addition, AFM indicates that the surface is very smooth with an RMS roughness of only 3.7 nm over a 5 x 5 micron area. However, in spite of recent theoretical predictions,@footnote 1@ we have yet to observe room temperature ferromagnetism in this material. These results differ from those recently obtained by Ueda et al. in which they show weak ferromagnetism that persists to ~300 K from similar PLD-grown films of slightly lower crystalline quality.@footnote 2@ We are currently performing below-room-temperature magnetic measurements to determine the exact value of the Curie temperature in our material. These results, as well as the effects of post-growth annealing will be presented at the conference. @FootnoteText@ @footnote 1@Sato et al., Japanese Journal of Applied Physics 40, L334-L336 (2001)@footnote 2@Ueda et al., Applied Physics Letters 79(7), 988-990 (2001).